Evaluation of resistance of wild species of Helianthus to high-virulent broomrape (Orobanche cumana Wallr.), affecting sunflower in Rostov region of Russian Federation

Wild species of sunflower from the collection of Kuban experimental station of VIR were trialed for the re-sistance to broomrape ( O. cumana Wallr.) of the most virulent population in Rostov region: 14 samples of annual and 27 – of perennial species. From the annual – only H. petiolaris had a weak degree of affection (1-3 tubercles for a plant), the others were affected in strong degree. The majority of the samples of perennial varieties had shown im-munity. This immunity is not connected with the absence of stimulating effect of root exudations on emergence of seedlings of parasite, which germinated successfully. The apical cells of seedlings penetrated into the roots of sun-flower, but the haustoria didn’t develop. The immunity is more likely to be connected with physiological-biochemical peculiarities of the root cortex cells.